In recent years, a cluster system for connecting a large number of nodes, for example, servers or the like through a high speed network is widely used in the HPC (High Performance Computer) field. In such a cluster system, a parallel computation processing is often carried out. For a communication in the parallel computation processing, it is demanded to ensure wide bandwidth and to obtain low latency in a signal transmission. In order to implement them, particularly, there is widely used a Fat Tree connection through InfiniBand in a large scale cluster system (see, for example, Using Fat-Trees to Maximize the Number of Processors in a Massively Parallel Computer, M. Valerio, L. E. Moser and P. M. Melliar-Smith, Department of Electrical and Computer Engineering University of California, Santa Barbara).
In the InfiniBand, there is a crossbar switch having a maximum 36-port structure. In the case in which a switch having a larger scale is used, there are used multiport switches 901 and 902 including a network having a plurality of switches connected through Fat Tree in two stages as illustrated in FIG. 11, and the like. FIG. 11 is a diagram illustrating a structure of a network device having a configuration of Fat Tree using a multiport switch.
The Fat Tree represents a topology of a network having a tree type network configuration which is multiplexed, for example, the structure illustrated in FIG. 11. In FIG. 11, the network has the multiport switches 901 and 902 and a switch in a lower stage which constitute two-stage Fat Tree. However, the multiport switches 901 and 902 further include the configuration of the Fat Tree. Therefore, there are logically three stages. In FIG. 11, a switch included in a region surrounded by a dotted line 911 is set to be a first stage switch, a switch included in a region surrounded by a dotted line 912 is set to be a second stage switch, and a switch included in a region surrounded by a dotted line 913 is set to be a third stage switch.
In the connection of the Fat Tree illustrated in FIG. 11, the connection of the second stage switch and the third stage switch is mounted in a housing of the multiport switch, and there is no fear of an erroneous connection.
On the other hand, the connection between the first stage switch and the second stage switch is singly carried out through a manual operation by a network manager. For this reason, there is a fear that an erroneous connection might be caused in a connection between the first stage switch and the second stage switch. In particular, a large number of cables are intensively provided on the multiport switch 901 and 902 sides. Therefore, there is a high possibility that the erroneous connection might be caused. For this reason, conventionally, the connection is checked after a connecting work is completed, and the connection is corrected and a new connection is thus constructed if the erroneous connection is detected. When a large scale InfiniBand network is to be constructed, particularly, the work for detecting and correcting the erroneous connection requires a large number of man-hours. Consequently, an efficiency of the network constructing work is reduced so that a time required for the work is prolonged.
As the erroneous connection, for example, a connection is carried out in a state in which paths are erroneously replaced with each other like paths 923 and 924 illustrated in the dotted line of FIG. 11 though paths 921 and 922 are to be originally obtained. In the case of the erroneous connection, when standard routing in the Fat Tree is carried out, a path competition is caused, that is, at least two signals are transmitted to a single path at the same time in a collective communication represented by an all-to-all communication. Consequently, a band through which the signal passes in the signal transmission is reduced. For this reason, even if a network is constructed to have the configuration of the Fat Tree in the case of the erroneous connection, there is a fear that a performance such as a signal transmitting speed might be deteriorated.